Adjusting the AFR is difficult, because during a burn, it varies widely, from super rich to super lean. This causes the engine not to want to start. Also, it's impossible to tune the AFR without the correct load. The carb has an AFR screw for the low end and the main needle for the high end. The carb needed the needle moved a bit, but once you do that, the AFR and idle screws need tuned a lot, making this a risky decision in the middle of a race day. You can only drive the car on the track, so you wouldn't get many chances to tune the engine if you messed it up. Also, the low end AFR screw is super sensitive, so it's hard to play with. Varying air temperature for the intake also makes things a challenge, as the car heats up once the lid is put on.... this year, the nose of the car got so hot under where the front window was, that it was getting soft. Some teams put aluminum foil under the driver's feet... I can't imagine that helps visibility out of the already sketchy windows.